linux-kernel - Re: [PATCH v3 00/11] iommu: Prepare to deliver page faults to user space

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Message-ID: <ZOOtjJLumarsBzwN@ziepe.ca>
Date:   Mon, 21 Aug 2023 15:31:40 -0300
From:   Jason Gunthorpe <jgg@...pe.ca>
To:     Lu Baolu <baolu.lu@...ux.intel.com>
Cc:     Joerg Roedel <joro@...tes.org>, Will Deacon <will@...nel.org>,
        Robin Murphy <robin.murphy@....com>,
        Kevin Tian <kevin.tian@...el.com>,
        Jean-Philippe Brucker <jean-philippe@...aro.org>,
        Nicolin Chen <nicolinc@...dia.com>,
        Yi Liu <yi.l.liu@...el.com>,
        Jacob Pan <jacob.jun.pan@...ux.intel.com>,
        iommu@...ts.linux.dev, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 00/11] iommu: Prepare to deliver page faults to user
 space

On Fri, Aug 18, 2023 at 07:40:36AM +0800, Lu Baolu wrote:
> When a user-managed page table is attached to an IOMMU, it is necessary
> to deliver IO page faults to user space so that they can be handled
> appropriately. One use case for this is nested translation, which is
> currently being discussed in the mailing list.
> 
> I have posted a RFC series [1] that describes the implementation of
> delivering page faults to user space through IOMMUFD. This series has
> received several comments on the IOMMU refactoring, which I am trying to
> address in this series.

Looking at this after all the patches are applied..

iommu_report_device_fault() and iommu_queue_iopf() should be put in
the same file.

iommu_queue_iopf() seems misnamed since it isn't queuing anything. It
is delivering the fault to the domain.

It is weird that iommu_sva_domain_alloc is not in the sva file

iopf_queue_work() wrappers a work queue, but it should trampoline
through another function before invoking the driver's callback and not
invoke it with a weird work_struct - decode the group and get back the
domain. Every single handler will require the group and domain.

Same for domain->iopf_handler, the domain should be an argument if we
are invoking the function on a domain.

Perhaps group->domain is a simple answer.

Jason